INVESTMENT SECURITIES (Details) (USD $)	Mar. 31, 2012	Dec. 31, 2011
Held-to-maturity portfolio [Abstract]
Amortized cost	$ 652,673,000	$ 553,495,000
Gross unrealized gains	57,338,000	64,340,000
Gross unrealized losses	1,998,000	0
Estimated fair value	708,013,000	617,835,000
Available-for-sale portfolio [Abstract]
Amortized cost	1,966,877,000	1,453,461,000
Gross unrealized gains	100,582,000	110,211,000
Gross unrealized losses	22,079,000	24,699,000
Total available-for-sale investment securities	2,045,380,000	1,538,973,000
Other Securities [Abstract]
Other investment securities, cost	67,092,000	58,902,000
Other investment securities , estimated fair value	67,092,000	58,902,000
Held-to-maturity securities in unrealized loss positions, number of positions [Abstract]
Held-to-maturity securities in unrealized loss positions for less than 12 months, number of positions	7
Held-to-maturity securities in unrealized loss positions 12 months or more, number of positions	0
Held-to-maturity securities in unrealized loss positions, number of positions	7
Held-to-maturity securities, Debt maturities, Fair value [Abstract]
Held-to-maturity securities, Unrealized Loss Position, Less than 12 months, Fair value	99,228,000
Held-to-maturity securities, Unrealized Loss Position, 12 Months or longer, Fair value	0
Held-to-maturity securities, Unrealized Loss Position, Fair Value	99,228,000
Held-to-maturity securities, Debt maturities, Gross unrealized losses [Abstract]
Held-to-maturity Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	1,998,000
Held-to-maturity Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	0
Held-to-maturity Securities, Unrealized Loss Position, Gross unrealized losses	1,998,000
Available-for-sale securities in unrealized loss positions, number of positions [Abstract]
Available-for-sale securities in unrealized loss positions for less than 12 months, number of positions	124	23
Available-for-sale securities in unrealized loss positions for more than 12 months, number of positions	22	12
Total available-for-sale securities in unrealized loss positions, number of positions	146	35
Available-for-sale securities, Debt maturities, Fair value [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Fair Value	118,597,000	9,397,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Fair Value	58,823,000	49,896,000
Available-for-sale Securities, Unrealized Loss Position, Fair Value	177,420,000	59,293,000
Available-for-sale securities, Debt maturities, Gross unrealized losses [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	2,268,000	190,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	19,811,000	24,509,000
Available-for-sale Securities, Unrealized Loss Position, Gross unrealized losses	22,079,000	24,699,000
Held-to-maturity, Amortized Cost [Abstract]
Held -to-maturity, Amortized Cost, Due in one year or less	12,525,000
Held -to-maturity, Amortized Cost, Due in one to five years	279,894,000
Held -to-maturity, Amortized Cost, Due in five through ten years	163,599,000
Held -to-maturity, Amortized Cost, Due after ten years	164,572,000
Held-to-maturity Securities, Amortized Cost, Subtotal	620,590,000
Held-to-maturity Collateralized Mortgage Obligations, Amortized Cost, without single maturity date	0
Held-to-maturity Mortgage Backed Securities, Amortized Cost, without single maturity date	32,083,000
Held-to-maturity, Amortized Cost	652,673,000
Held-to-maturity, Fair value [Abstract]
Held-to-maturity, Fair value, Due in one year or less	12,615,000
Held-to-maturity, Fair value, Due in one to five years	307,866,000
Held-to-maturity, Fair value, Due in five through ten years	183,466,000
Held-to-maturity, Fair value, Due after ten years	170,287,000
Held-to-maturity Securities, Fair Value, Subtotal	674,234,000
Held-to-maturity Collateralized Mortgage Obligations, Fair Value, without single maturity date	0
Held-to-maturity Mortgage Backed Securities, Amortized Cost, without single maturity date	33,779,000
Held-to-maturity, Fair value	708,013,000
Available-for-sale securities, Amortized Cost [Abstract]
Available-for-sale securities, Amortized Cost, Due in one year or less	31,089,000
Available-for-sale securities, Amortized Cost, Due in one to five years	228,714,000
Available-for-sale securities, Amortized Cost, Due in five through ten years	885,741,000
Available-for-sale securities, Amortized Cost, Due after ten years	484,540,000
Available-for-sale Securities, Amortized Cost, with a single maturity date, Subtotal	1,630,084,000
Available-for-sale government agency collateralized mortgage obligations, amortized cost, without a single maturity date	41,726,000
Available-for-sale government agency mortgage-backed securities, amortized cost, without a single maturity date	294,686,000
Available-for-sale securities, Amortized Cost	1,966,496,000
Available-for-sale securities, Fair value [Abstract]
Available-for-sale securities, Fair value, Due in one year or less	31,342,000
Available-for-sale securities, Fair value, Due in one to five years	243,293,000
Available-for-sale securities, Fair value, Due in five through ten years	917,083,000
Available-for-sale securities, Fair value, Due after ten years	495,857,000
Available-for-sale Securities, Fair Value, Subtotal	1,687,575,000
Available-for-sale government agency collateralized mortgage obligations, fair value, without single maturity date	43,310,000
Available-for-sale government agency mortgage-backed securities, fair value, without single maturity date	314,077,000
Available-for-sale securities, Fair value	2,044,962,000
Total Securities, Unrealized Loss Position, Number of Positions [Abstract]
Total securities in unrealized loss positions for less than 12 months, number of positions	131
Total securities in unrealized loss positions for 12 months or longer, number of positions	22
Total securities in unrealized loss positions, number of positions	153
Total Securities, Unrealized Loss Position, Fair Value [Abstract]
Total Securities, Unrealized Loss Position, Less than 12 Months, Fair Value	217,825,000
Total Securities, Unrealized Loss Position, 12 Months or Longer, Fair Value	58,823,000
Total Securities, Unrealized Loss Position, Fair Value	276,648,000
Total Securities, Unrealized Loss Position, Gross unrealized losses [Abstract]
Total Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	4,266,000
Total Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	19,811,000
Total Securities, Unrealized Loss Position, Gross unrealized losses	24,077,000
Pooled trust preferred, class A-1 securities, par value	68,600,000
Pooled trust preferred, class A-1 securities, unrealized losses	19,700,000
Percentage minimum for underlying collateral to be in deferral or default concurrently before non-receipt of contractual cash flows (in hundredths)	37.00%
Percentage maximum for underlying collateral to be in deferral or default concurrently before non-receipt of contractual cash flows (in hundredths)	38.00%
US Treasury and Agency Securities [Member]
Held-to-maturity portfolio [Abstract]
Amortized cost	546,636,000	448,260,000
Gross unrealized gains	50,127,000	56,800,000
Gross unrealized losses	1,968,000	0
Estimated fair value	594,795,000	505,060,000
Available-for-sale portfolio [Abstract]
Amortized cost	927,036,000	463,922,000
Gross unrealized gains	49,971,000	56,626,000
Gross unrealized losses	104,000	0
Total available-for-sale investment securities	976,903,000	520,548,000
Held-to-maturity securities in unrealized loss positions, number of positions [Abstract]
Held-to-maturity securities in unrealized loss positions for less than 12 months, number of positions	5
Held-to-maturity securities in unrealized loss positions 12 months or more, number of positions	0
Held-to-maturity securities in unrealized loss positions, number of positions	5
Held-to-maturity securities, Debt maturities, Fair value [Abstract]
Held-to-maturity securities, Unrealized Loss Position, Less than 12 months, Fair value	96,318,000
Held-to-maturity securities, Unrealized Loss Position, 12 Months or longer, Fair value	0
Held-to-maturity securities, Unrealized Loss Position, Fair Value	96,318,000
Held-to-maturity securities, Debt maturities, Gross unrealized losses [Abstract]
Held-to-maturity Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	1,968,000
Held-to-maturity Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	0
Held-to-maturity Securities, Unrealized Loss Position, Gross unrealized losses	1,968,000
Available-for-sale securities in unrealized loss positions, number of positions [Abstract]
Available-for-sale securities in unrealized loss positions for less than 12 months, number of positions	2
Available-for-sale securities in unrealized loss positions for more than 12 months, number of positions	0
Total available-for-sale securities in unrealized loss positions, number of positions	2
Available-for-sale securities, Debt maturities, Fair value [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Fair Value	34,365,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Fair Value	0
Available-for-sale Securities, Unrealized Loss Position, Fair Value	34,365,000
Available-for-sale securities, Debt maturities, Gross unrealized losses [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	104,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	0
Available-for-sale Securities, Unrealized Loss Position, Gross unrealized losses	104,000
Government Agency Mortgage-Backed Securities [Member]
Held-to-maturity portfolio [Abstract]
Amortized cost	32,083,000	35,576,000
Gross unrealized gains	1,696,000	2,452,000
Gross unrealized losses	0	0
Estimated fair value	33,779,000	38,028,000
Available-for-sale portfolio [Abstract]
Amortized cost	294,686,000	310,541,000
Gross unrealized gains	19,416,000	20,840,000
Gross unrealized losses	25,000	2,000
Total available-for-sale investment securities	314,077,000	331,379,000
Available-for-sale securities in unrealized loss positions, number of positions [Abstract]
Available-for-sale securities in unrealized loss positions for less than 12 months, number of positions	3	3
Available-for-sale securities in unrealized loss positions for more than 12 months, number of positions	1	0
Total available-for-sale securities in unrealized loss positions, number of positions	4	3
Available-for-sale securities, Debt maturities, Fair value [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Fair Value	3,421,000	2,415,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Fair Value	30,000	0
Available-for-sale Securities, Unrealized Loss Position, Fair Value	3,451,000	2,415,000
Available-for-sale securities, Debt maturities, Gross unrealized losses [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	24,000	2,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	1,000	0
Available-for-sale Securities, Unrealized Loss Position, Gross unrealized losses	25,000	2,000
Obligations of State and Political Subdivisions [Member]
Held-to-maturity portfolio [Abstract]
Amortized cost	70,987,000	69,623,000
Gross unrealized gains	5,515,000	5,088,000
Gross unrealized losses	0	0
Estimated fair value	76,502,000	74,711,000
Available-for-sale portfolio [Abstract]
Amortized cost	614,466,000	543,527,000
Gross unrealized gains	28,162,000	29,721,000
Gross unrealized losses	2,130,000	236,000
Total available-for-sale investment securities	640,498,000	573,012,000
Available-for-sale securities in unrealized loss positions, number of positions [Abstract]
Available-for-sale securities in unrealized loss positions for less than 12 months, number of positions	116	2
Available-for-sale securities in unrealized loss positions for more than 12 months, number of positions	6	6
Total available-for-sale securities in unrealized loss positions, number of positions	122	8
Available-for-sale securities, Debt maturities, Fair value [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Fair Value	80,605,000	211,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Fair Value	6,238,000	6,038,000
Available-for-sale Securities, Unrealized Loss Position, Fair Value	86,843,000	6,249,000
Available-for-sale securities, Debt maturities, Gross unrealized losses [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	2,096,000	0
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	34,000	236,000
Available-for-sale Securities, Unrealized Loss Position, Gross unrealized losses	2,130,000	236,000
Pooled Trust Preferred Securities [Member]
Available-for-sale portfolio [Abstract]
Amortized cost	67,087,000	68,115,000
Gross unrealized gains	0	0
Gross unrealized losses	19,702,000	24,269,000
Total available-for-sale investment securities	47,385,000	43,846,000
Available-for-sale securities in unrealized loss positions, number of positions [Abstract]
Available-for-sale securities in unrealized loss positions for less than 12 months, number of positions	0	0
Available-for-sale securities in unrealized loss positions for more than 12 months, number of positions	3	3
Total available-for-sale securities in unrealized loss positions, number of positions	3	3
Available-for-sale securities, Debt maturities, Fair value [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Fair Value	0	0
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Fair Value	47,385,000	43,846,000
Available-for-sale Securities, Unrealized Loss Position, Fair Value	47,385,000	43,846,000
Available-for-sale securities, Debt maturities, Gross unrealized losses [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	0	0
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	19,702,000	24,269,000
Available-for-sale Securities, Unrealized Loss Position, Gross unrealized losses	19,702,000	24,269,000
Corporate Debt Securities [Member]
Held-to-maturity portfolio [Abstract]
Amortized cost	2,940,000	0
Gross unrealized gains	0	0
Gross unrealized losses	30,000	0
Estimated fair value	2,910,000	0
Available-for-sale portfolio [Abstract]
Amortized cost	21,495,000	21,495,000
Gross unrealized gains	1,294,000	1,360,000
Gross unrealized losses	0	0
Total available-for-sale investment securities	22,789,000	22,855,000
Held-to-maturity securities in unrealized loss positions, number of positions [Abstract]
Held-to-maturity securities in unrealized loss positions for less than 12 months, number of positions	2
Held-to-maturity securities in unrealized loss positions 12 months or more, number of positions	0
Held-to-maturity securities in unrealized loss positions, number of positions	2
Held-to-maturity securities, Debt maturities, Fair value [Abstract]
Held-to-maturity securities, Unrealized Loss Position, Less than 12 months, Fair value	2,910,000
Held-to-maturity securities, Unrealized Loss Position, 12 Months or longer, Fair value	0
Held-to-maturity securities, Unrealized Loss Position, Fair Value	2,910,000
Held-to-maturity securities, Debt maturities, Gross unrealized losses [Abstract]
Held-to-maturity Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	30,000
Held-to-maturity Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	0
Held-to-maturity Securities, Unrealized Loss Position, Gross unrealized losses	30,000
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale portfolio [Abstract]
Amortized cost	41,726,000	45,481,000
Gross unrealized gains	1,655,000	1,572,000
Gross unrealized losses	71,000	110,000
Total available-for-sale investment securities	43,310,000	46,943,000
Available-for-sale securities in unrealized loss positions, number of positions [Abstract]
Available-for-sale securities in unrealized loss positions for less than 12 months, number of positions	2	17
Available-for-sale securities in unrealized loss positions for more than 12 months, number of positions	9	0
Total available-for-sale securities in unrealized loss positions, number of positions	11	17
Available-for-sale securities, Debt maturities, Fair value [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Fair Value	49,000	6,648,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Fair Value	5,157,000	0
Available-for-sale Securities, Unrealized Loss Position, Fair Value	5,206,000	6,648,000
Available-for-sale securities, Debt maturities, Gross unrealized losses [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	0	110,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	71,000	0
Available-for-sale Securities, Unrealized Loss Position, Gross unrealized losses	71,000	110,000
Marketable Equity Security [Member]
Available-for-sale portfolio [Abstract]
Amortized cost	381,000	380,000
Gross unrealized gains	84,000	92,000
Gross unrealized losses	47,000	82,000
Total available-for-sale investment securities	418,000	390,000
Available-for-sale securities in unrealized loss positions, number of positions [Abstract]
Available-for-sale securities in unrealized loss positions for less than 12 months, number of positions	1	1
Available-for-sale securities in unrealized loss positions for more than 12 months, number of positions	3	3
Total available-for-sale securities in unrealized loss positions, number of positions	4	4
Available-for-sale securities, Debt maturities, Fair value [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Fair Value	217,000	123,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Fair Value	13,000	12,000
Available-for-sale Securities, Unrealized Loss Position, Fair Value	170,000	135,000
Available-for-sale securities, Debt maturities, Gross unrealized losses [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	44,000	78,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	3,000	4,000
Available-for-sale Securities, Unrealized Loss Position, Gross unrealized losses	47,000	82,000
Federal Reserve Bank Stock [Member]
Other Securities [Abstract]
Other investment securities, cost	15,450,000	15,451,000
Other investment securities , estimated fair value	15,450,000	15,451,000
Federal Home Loan Bank Stock [Member]
Other Securities [Abstract]
Other investment securities, cost	46,534,000	38,343,000
Other investment securities , estimated fair value	46,534,000	38,343,000
Other Equity Securities [Member]
Held-to-maturity portfolio [Abstract]
Amortized cost	27,000	36,000
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Estimated fair value	27,000	36,000
Other Securities [Abstract]
Other investment securities, cost	5,108,000	5,108,000
Other investment securities , estimated fair value	$ 5,108,000	$ 5,108,000